Understanding Reflection of Light

• Sight enables perceiving mountains, rivers, trees, plants, chairs, people, clouds, rainbows, birds, the moon, and stars

How Seeing Works

• Eyes alone are insufficient for sight
• Light must enter our eyes from an object for it to be visible
• Light can be emitted by the object or reflected off it

Reflection

• Polished or shiny surfaces act as mirrors
• A mirror alters the direction of light

Laws of Reflection Activity

• Comb with one opening is used to create a light ray from a torch
• A plane mirror is placed in the ray's path to observe reflection

Incident and Reflected Rays

• The light ray striking a surface is the incident ray
• The ray bouncing back is the reflected ray

Idealization of Light

• A ray of light is an idealization because light is a narrow beam made of rays
• The term "ray" is used for simplicity to refer to a narrow beam

Defining the Normal

• A line drawn at 90° to the mirror where the incident ray strikes is called the normal

Angles of Incidence and Reflection

• The angle between the normal and incident ray is the angle of incidence (∠i)
• The angle between the normal and reflected ray is the angle of reflection (∠r)

Law of Reflection

• The angle of incidence equals the angle of reflection

Laws of Reflection Activity 2

• Stiff paper is used to observe a reflected ray.
• Bending the part of the paper where the reflected ray falls affects visibility

Laws of Reflection

• The incident ray, normal, and reflected ray all lie in the same plane

Light Sources

• The Sun can be used as a light source for reflection activities
• Ray Streak Apparatus can also be used for these activities

Plane Mirror Images

• Plane mirrors create images with specific characteristics
• Images are erect, same size as the object, appear at the same distance behind the mirror as the object is in front, and cannot be obtained on a screen

Virtual Images

• Reflected rays from a plane mirror seem to originate from a point behind the mirror
• These rays do not actually meet, but instead are a virtual image
• Virtual images cannot be obtained on a screen

Lateral Inversion

• Plane mirror images have left and right sides reversed, called lateral inversion

Regular Reflection

• Parallel incident rays on an irregular surface are reflected in different directions

Diffused Reflection

• Reflection from a rough surface scatters light and known as diffused or irregular reflection
• Diffused reflection is due to irregularities not a failure of laws of reflection

Regular Reflection

• Reflection from smooth surfaces creates regular reflection and forms images

Reflected Light and Vision

• Most objects are visible due to reflected light
• The moon reflects sunlight
• Objects shining by reflected light are illuminated objects

Luminous Objects

• Objects that emit their own light are called luminous objects
• Examples of luminous objects, the Sun, fire, a candle flame, and an electric lamp

Periscopes

• Periscopes use two plane mirrors to view objects indirectly
• They enable seeing objects not visible directly, used in submarines, tanks, and bunkers

Multiple Images

• Plane mirrors create single images
• Combinations of mirrors can produce multiple images

Kaleidoscope

• Multiple images from angled mirrors are used, creating visually appealing patterns
• It uses three rectangular mirror strips to be made

Sunlight

• Sunlight is white light, composed of seven colours

Eyes

• Eyes are essential sense organs and require understanding of their structure and function

Eye Anatomy

• Cornea: The transparent outer layer
• Iris: The coloured part of the eye, controlling pupil size
• Pupil: The opening in the iris that regulates light entry

Pupil Size

• Pupil size adjusts to control light entering the eye

Lens

• The lens focuses light onto the retina

Retina

• The layer at the back of the eye containing nerve cells

Types of Cells in the Retina

• Cones: Sensitive to bright light and color
• Rods: Sensitive to dim light

Blind Spot

• The junction of optic nerve and retina has no sensory cells, creating a blind spot

Image Persistence

• The impression of an image persists for about 1/16th of a second

Movie Perception

• Movies use a series of still images flashed rapidly to create motion

Eyelids

• Eyelids protect eyes from objects and control light exposure

Eye Accommodation

• Eyes adjust focus for near and distant objects

Reading Distance

• The comfortable reading distance for a normal eye is about 25 cm

Vision Defects

• Corrective lenses can fix vision problems

Cataracts

• Cataracts cause foggy eyesight due to cloudy lens and it require surgery for insertion of opaque lens

Eye Care

• Regular check-ups with an eye specialist, and use spectacles should there is a need

Lighting

• Too little or too much is harmful
• Insufficient light causes strain
• Excessive light is harmful

Diet

• A balanced diet, including Vitamin A, is crucial for eye health
• Vitamin A sources: carrots, broccoli, green vegetables, cod liver oil, eggs, milk, curd, cheese, butter, papaya, and mango

Visually Impaired

• Visually impaired individuals develop heightened senses
• They also use additional resources for capabilities development

Resources for Visually Impaired

• Non-optical aids include visual, tactual, auditory, and electronic aids
• Optical aids include lenses, magnifiers, and telescopic aids

Braille System

• The Braille system is the most popular resource for visually challenged individuals
• Louis Braille developed it
• The Braille system utilizes 63 dot patterns or characters

Braille Code Application

• Braille code represents letters, words, or grammatical signs
• It is used for languages, math, and scientific notation